William (Bill) David Mensch, Jr.,

A central person in the creation of the Motorola 6800 and MOS Technology 6502 families of microprocessor chips, Mensch is also recognized as the sole IC design engineer of the 6820/21 PIA, the first peripheral IC to have bit-programmable I/O. An American engineer born in Quakertown, Pennsylvania, he graduated with an associate's degree from Temple University in 1966, and received his bachelor's degree in electrical engineering from the University of Arizona in Tucson in 1971. Mensch has taught classes at Arizona State University, including courses on system-on-a-chip (SoC) IC design, and has been a Senior Member of the IEEE.

Before founding the Western Design Center in 1978, he held design engineering and management positions at Philco-Ford, Motorola, MOS Technology, and Integrated Circuit Engineering. Mensch later worked primarily on extending and expanding the latter architecture at the Western Design Center. Along with three other engineers at MOS Technology, he held the patent on the decimal correct circuitry on the 6502 CPU.

He was responsible for the basic circuit design, transistor sizing, instruction decode logic (wishing to minimize the number of levels of logic so as to achieve higher speed operation), oscillator design, and buffer design. His first major effort along with his team at the Western Design Center was the development of the WDC 65C02, a bug-fixed version of the 6502 CPU implemented in CMOS circuit technology (the original 6502 was made in NMOS). Later, a fully compatible, 16-bit extension of the 6502 family, called the 65816, became an important product of the company. Further information on related products is available in the article about WDC.

The Western Design Center produced a hobbyist computer system called the Mensch Computer, based on the WDC 65C265 microcontroller, which implemented both the 16-bit instruction set of the W65C816/65816 microprocessor and the 8-bit instruction set of the 6502 microprocessor. Mensch also produced the Mensch Works suite of software to accompany it. He wrote the upcoming Terbium processor family's data sheets and made the major RTL design decisions associated with that processor architecture.

In 2004, Mensch was inducted into the Computer Hall of Fame, hosted by the San Diego Computer Museum, part of the San Diego State University Library. In 2005, he was presented with a Lifetime Achievement Award from the University of Arizona's College of Engineering. He has remained involved with design engineering at WDC in addition to his work as CEO.